1. A day characterized by sadness, sorrow, or disappointment experienced by the person being addressed
Today has been a sad day for you, and I'm sorry to hear that.
Hoje foi um dia triste para você, e sinto muito em saber disso.
2. An unfortunate or unhappy day in someone's life; a day marked by grief or loss
It was a sad day for you when you heard the news.
Foi um dia triste para você quando recebeu a notícia.